2+ 3b = 5b - 2(2b + 3) how do you solve for b?

-2 + 3b = 5b - 2(2b + 3)  Distribute the -2 through the parentheses.
-2 + 3b = 5b - 4b - 6        Combine like terms
-2 + 3b = b - 6                 Bring all "b's" to one side of the equation
-2 + 3b - b = b - b - 6       Combine like terms
-2 + 2b = -6                      Bring the 2 to the right side of the equation
-2 + 2 + 2b = -6 + 2          Combine like terms
2b = -4                              Isolate b by dividing both sides by 2
b = -4/2 = -2

Answer b = -2

The density of the cube is 40